Stereo‐Complementary Two‐Step Cascades Using a Two‐Enzyme System Leading to Enantiopure Epoxides

Abstract

A novel one-pot, two-step, two-enzyme cascade is described. Pro-chiral a-chloro ketones are stereoselectively reduced to the corresponding halohydrins as an intermediate by a biocatalytic hydrogen transfer process. The intermediate is transformed to the corresponding epoxide by a non-enantioselective halohydrin dehalogenase. Thus, by combining a Prelog-or anti-Prelog alcohol dehydrogenase with a non-selective halohydrin dehalogenase, enantiopure (R)-as well as (S)-epoxides were obtained.

Highly Efficient Chemoenzymatic Synthesis of Methyl (R)‐o‐Chloromandelate, a Key Intermediate for Clopidogrel, via Asymmetric Reduction with Recombinant Escherichia coli

“…The organic layer was dried over MgSO 4 and concentrated. The product was purified by basic alumina column chromatography (hexane/EtOAc, 10:1-0:1) to afford ethyl o-chlorobenzoylformate [7] as a pale yellow oil; yield: 1.42 g (44% ( 10). Centrifugation (20,000 rpm, 4 8C, 30 min) gave a cell-free extract (CFE) as the supernatant.…”

“…[1, 2,10] We have been studying a versatile carbonyl reductase called SCR capable of showing catalytic activity for various ketones, such as a-chloro ketones, a-acetoxy ketones, a-keto esters, b-keto esters, g-keto esters, and b-diketones, and 13 out of 20 alcohols obtained had enantiomeric purities of > 98% ee. [11] The gene encoding SCR has been cloned and expressed in E. coli, and the asymmetric reduction of various ketones with the recombinant E. coli cells has afforded 20 synthetically useful alcohols, 11 of which had enantiomeric purities of > 98% ee.…”

Cell-free Biosystems in the Production of Electricity and Bioenergy

“…The first pattern is linear, where the product from the first reaction becomes the substrate for the next reaction and a series of cascade enzymes together have a linear reaction system. Most synthetic processes regardless of chemical or biological conversions belong to this pattern [40,41]. The second pattern is linear branch, where desired products are generated from ''branches'' in a linear enzymatic pathway.…”

Practical Two‐Step Synthesis of an Enantiopure Aliphatic Terminal (S)‐Epoxide Based on Reduction of Haloalkanones with “Designer Cells”

“…[11] A subsequent publication by Kroutil et al describes the two-stage biocatalytic synthesis of highly enantiopure (S)-1-octene oxide, albeit at chemical yields of only 34 % for each of the two steps. [13] In continuation of our studies on the use of tailormade whole-cell biocatalysts for the preparation of optically active alcohols, [14,15] in the following we report a practical and efficient process for the highly enantioselective synthesis of aliphatic (S)-halohydrins, running at high substrate concentrations of > 100 g/L. The cofactor is regenerated by means of an enzymecoupled approach.…”